1) Field of the Invention
The present invention relates to a method of preparing monoatomic layer black phosphorous having a single crystal structure by irradiating an ultrasound.
2) Background of Related Art
Graphene, which is a representative 2-D layer material, has higher electrical conductivity, electron mobility 100 times faster than that of silicon mainly used for a semiconductor, strength 100 times stronger than that of steel, and excellent thermal conductivity. Accordingly, studies and researches have been performed on the graphene. However, the graphene has a closed band structure in which the direct bandgap of electrons is insufficiently formed between a valance band and a conductive band. Accordingly, studies and researches have been performed toward fields, such as an electrode, heat transfer, and EM suppression, which facilitate applications, in addition to an active area of a semiconductor device due to the inherent limitation of the material.
The studies and researches have deeply performed on a nano-semiconductor device having high mobility using a chalcogenide-based material, such as MoS or WS, which is recently spotlighted and a 2-D layer material having an open band structure. When the chalcogenide-based compound is decomposed to a single layer or less, the chalcogenide-based compound may be used for a direct-bandgap semiconductor. However, since the chalcogenide-based compound has a limitation of serving as a compound of heterogeneous elements, the chalcogenide-based compound may not form a large-area material used to prepare a pure material and produce an electronic device.
To substitute for the chalcogenide-based material, phosphorene has been found out, and the phosphorene has a structure similar to that of carbon-based graphene, includes phosphorous atoms, has higher mobility, and serves as the 2-D material. The phosphorene may be delaminated from a black phosphorous crystal through a mechanical exfoliation (tapping) method in the same manner that a graphene layer is mechanically delaminated from a bulk of graphite. However, there are not developed a method of delaminating the black phosphorous to a monoatomic layer to obtain a single crystal similarly to that of the graphene.
As the related art, there is Korean Patent Registration No. 10-0788487 (issued on Dec. 17, 2007) entitled “Method for preparing black Phosphorus and black Phosphorus-carbon composites, prepared black Phosphorus and black Phosphorus-carbon composites and lithium rechargeable battery including the same, and method for using the rechargeable battery”.